All about Domains and Sub-Domains

Domains can be confusing to non-webby people, and it can be hard for webby people to explain it in a way that makes sense…

What is a domain?

Most simply a domain is what makes your web address unique. If you look in the address bar while looking at this post you’ll see it starts with The important bit there is ‘‘ – that is my domain. A domain is made up of a unique name for your site with the addition of a ‘domain extension’ – that’s the bit at the end. In my case it’s ‘’. There are lots of options for the domain extension – some are intended to represent the type of business, geographical location or topic of the site.

Choosing a domain

So when you’re thinking about a web address for your site, you need to think about the domain name and the domain extension and make sure that they both represent your site as well as possible.

Once you know what you want your site address to be you’ll have to find out if it’s available. It’s not possible for more than one site to have the same address so if someone else has already bought the domain you’d like, you’ll have to think of something else.

You can check domain availability via

Buying a domain

When you have found the domain you want, and have checked that it’s available, then next step is to buy it. Where you buy it depends on preference but to make life simpler for you the ideal would be to have your hosting and your domain with the same company. For example if your site is going to be run on, then the easiest way to get your domain is by purchasing it through It’s not compulsory to keep domains and hosts together though so shop around if you prefer.

You can transfer a domain to another domain company if necesary to keep your domain and hosting together. For example I originally bought my domain at 123-reg, but since I got hosting at, I transferred my domain to them to keep things organised.

If you already have a domain you can map it to a site by purchasing the domain mapping upgrade and changing the name servers for your domain at your domain company.


You may have noticed that my site address ( has an extra bit at the start. It has ‘web.’ before ‘’. This is called a sub-domain. It’s still part of my website and you can see that by the ‘’ part. In order to split my site up into chunks I’ve created this sub-domain for my web thoughts blog, and I also have another sub-domain for my other blog (about my photography). If you have sub-domains you can point them at different places. So points to and points to I also have a site at the main domain address of One domain, and 3 different parts.

If you’d like to use sub-domains to point to sites, you’ll need to purchase the domain mapping upgrade at and then create a CNAME entry for the sub-domain at the company where you bought it.

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